But public confidence in the Crown Prosecution Service's (CPS) willingness to prosecute VIPs was shaken when it announced that it would not prosecute Labour peer Lord Greville Janner, 86, despite having enough evidence, because he has dementia.

Mr Bailey also warned the arrival of superfast internet is likely to see "more and more" abuse of youngsters, including the live-streaming of abuse on the internet.He said predators have attempted to groom hundreds of thousands of children in Britain through internet sites and chat rooms.

"We assess there might be 50,000 people who are viewing indecent images of children online,” he said.

Speaking at the Police Federation annual conference in Bournemouth, Mrs May said: “We will need to face up to the changing nature of crime and the impact on police forces, including the much greater reporting of previously ignored or under-reported crimes such as child sexual abuse.

"I have said before that what we are seeing is only the tip of the iceberg.

"So let me be clear, I am committed to ensuring the police have the resources they need to investigate these appalling crimes and bring perpetrators to justice."

But Jon Brown, the lead on tackling sexual abuse at the NSPCC charity said: "There is not enough provision, and as far as adult survivors of abuse are concerned it is extremely patchy.”